Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.89	6.268%	$202.855	$202.86	$202.85	$202.90
Purchase #2	$63.56	13.355%	$72.0484	$72.05	$72.05	$72.00
Purchase #3	$126.26	10.802%	$139.8986	$139.90	$139.90	$139.90
Purchase #4	$28.94	12.250%	$32.4852	$32.49	$32.50	$32.50
Purchase #5	$20.27	6.505%	$21.5886	$21.59	$21.60	$21.60
Purchase #6	$31.31	8.842%	$34.0784	$34.08	$34.10	$34.10
Purchase #7	$246.51	4.603%	$257.8569	$257.86	$257.85	$257.90
7 purchase totals =	$707.74		$760.8111	$760.83	$760.85	$760.90